This invention relates in general to a method and apparatus for.the automated inspection of yarn packages (a.k.a. bobbins and filament bobbins), and specifically to a method and apparatus for the automated inspection of yarn packages to detect overthrows, broken filaments, and loops.
Yarns are typically produced by extruding, drawing, twisting or entangling filaments of the yarn through a series of wheels, chambers, rings, applicators, and godets, and then wound up on a spool, or tube, by a winder. Once the tube is wound with yarn, the resulting package is taken off the winder and made ready for shipment. Currently, packages are inspected for defects and conformity to specifications by human operators and, in some selected cases, automated inspection systems.
One known automated inspection system utilizes laser triangulation for the detection of certain which, while capable of detecting overthrown ends, loops, and broken filaments, suffers in that it lacks repeatability and accuracy, and cannot distinguish between these three defects. Also, due to the high amount of image processing required after the surface profile is produced, inspection speed is prohibitively low.
Another known automated inspection system has been described in U.S. Pat. No. 5,138,151 issued to Inada, et al. on Aug. 11, 1992. As disclosed by Inada, a CCD camera records light which has reflected off of yarn strands as a yarn package is rotated. The recorded image is then processed and any straight line image having a length exceeding a predetermined length is considered to be indicative of a defective yarn strand. As the Inada patent relies on the proper angular alignment of incident light to the yarn package, as well as comparisons between successive reflections of light off of yarn strands, the rate of missed defects and falsely identified defects is unacceptably high.
With the forgoing problems and concerns in minds, it is the general object of the present invention to provide an automated inspection method and apparatus which significantly improves upon the detection capabilities and speed of known systems with respect to overthrows, broken filaments, and loops.
It is an object of the present invention to provide a method and apparatus for the automated inspection of yarn packages.
It is another object of the present invention to provide a method and apparatus for the automated detection of overthrows on yarn packages.
It is another object of the present invention to provide a method and apparatus for illuminating the top and bottom of a yarn package with light and for capturing the images with a light sensor.
It is another object of the present invention to provide an algorithm and image processing method to convert a greyscale video image to a binary (black and white) image prior to the algorithmic detection of overthrows.
It is another object of the present invention to provide an algorithm and image processing method to detect overthrows from binary images by searching for straight vertical lines of continuous white pixels.
It is another object of the present invention to provide a method for selecting a trapezoidal, box, or combination Region of Interest (ROI) within the overthrow images in order to detect all of the aforementioned variations of overthrows.
It is another object of the present invention to provide a method and apparatus for the automated detection and measurement of broken filaments and loops on yarn packages.
It is another object of the present invention to provide a method and apparatus for illuminating the top, side, and bottom of a yarn package with a rectangular region of light and for capturing these illuminated regions with a light sensor.
It is another object of the present invention to provide an algorithm and image processing method to search for straight vertical white lines extending from the white base lines, where the straight vertical white line is a broken filament.
It is another object of the present invention to provide an algorithm and image processing method to search for black gaps between white pixels, where the top white pixel is a broken filament or loop, and the bottom white pixel, or pixel region, is the white base line.
It is another object of the present invention to provide an algorithm and image processing method to search for enclosed black pixels within the white base region.
It is another object of the present invention to provide a method and apparatus for the representation of overthrows, broken filaments, and loops in a defect image plot similar in style to that of a radar screen.
According to one embodiment of the present invention, a filament inspection method for detecting abnormalities in a wound yarn package includes illuminating the yarn package while sensing and recording an image of the illuminated yarn package. The method further includes evaluating the recorded image in accordance with predetermined criteria to determine thereby whether the recorded image indicates the presence of any abnormalities in the yarn package.